It seems that Mercurial and Mozilla have quite different patch/review process, but then again they’re two very different projects. I just found out today that Bug 394650 – Make line numbers linkable when viewing files/annotate for hg.mozilla.org [bugzilla.mozilla.org] was “works for me.” I was confused for a little bit; but yes indeed, annotate/changeset views on hg.mozilla.org have linkable line numbers for each file… just like how I would have coded it. 😉

Turns out that the patch that I sent in to the dev list ended up making it in to Mercurial 1.0 [hg.intevation.org]. No official reviews, no comments. They just checked in the patch to their “crew” (trunk) repository and let it bake for several months. Seems like nobody complained enough to have it backed out and here it is now in Mercurial 1.0 as we can see on hg.mozilla.org.

But this post isn’t about the differences between Mercurial and Mozilla. It’s about the current Mozilla CVS development process vs Mozilla with Mercurial.

One main difference is changesets. Instead of having a separate version number for each file as in CVS, all related changes are grouped together for a changeset. These are the steps one needs to do right now to see all related changes of a patch: 1) use mxr to find the file you’re editing 2) switch to blame to find the checkin 3) click the bug number if provided 4) hope there’s a clearly marked patch as the one checked in to see what else was changed. 🙁

With Mercurial, you can just look at the changeset which contains everything; e.g., patch to not need to click the page to use gmail keyboard commands [hg.mozilla.org]. Additionally, now with my patch for showing line numbers in changesets, you can link people to a specific line in a patch [hg.mozilla.org]. This could be useful if you need to point to a particular line in a bugzilla comment about why it broke something. Or especially useful with a stack of patches on mq and you’re collecting feedback on it from other people.

Another aspect of changesets is that there’s a “global version” for the whole repository. You can jump back in time to an earlier revision and view the whole repository as it was before a particular patch was checked in. We currently have something like this on a per-file basis with bonsai, but you need to do so much more work to look at “the right version” of other files. E.g., going back to when adaptive learning was checked in [hg.mozilla.org], you can see that the autocomplete was still only emphasizing the first match in the url and title [hg.mozilla.org].

Of course, you can just use the mercurial web interface to view the latest version of the file. Just take http://hg.mozilla.org/cvs-trunk-mirror/index.cgi/file/tip/ and append the file you want. (Normally “tip” would be a changeset/revision hex number, but you can put in “tip” because it’s an alias (tag) for the latest version.) And from there, you can look at the whole patch for the current version (changeset), browse the checkin history of that file (revisions), or look at the blame (annotate) [unfortunately it doesn’t have checkin comments on hover yet].

Typing out that whole url might be cumbersome, but good thing we have the AwesomeBar with multi-word search on word boundaries (with camel case) plus adaptive learning. 😉 “hg. auto” [hg.mozilla.org]

I’m not sure how distributed the development process will become for Mozilla, but these neat tools provided by default with Mercurial will make it easier to track changes and refer to them in bugzilla comments or over IRC. (Oh, and if you’re using mercurial and haven’t looked into mq yet, you should do so. It’s a great (builtin) extension to track/reorder multiple patches that you’re working on. And for those curious how I send changes for try-server builds, I apply the stack of patches and hg export firstpatch:lastpatch > combined.patch 😀 )

I’ve been busy preparing for a conference talk, so I didn’t get around to reporting AwesomeBar improvements for Beta 5 sooner. (But for those curious, I presented Branch-on-Random [pdf, uiuc.edu] at CGO 2008 [cgo.org] (Code Generation and Optimization). Basically, it’s an instruction that’s really cheap to implement and allows for a factor of 10 times less overhead than traditional sampling techniques. I think it went well, and I even got asked during Q&A.. “When can I buy one of these?” 🙂 )

As we’re winding down to ship Firefox 3, there aren’t as many more big features, but there’s still some useful changes in Beta 5 in terms of functionality, display, and performance. So those of you who have installed extensions to make the auto-complete smaller might want to turn it off to try out the new look.

Functionality

To better accommodate people’s expectations of results in the auto-complete, there are frecency tweaks to better prefer pages you’ve typed — by default, before adaptive learning. This helps address concerns that the top level site’s main page should appear high in the list because typically people are typing in the domain.

Another common complaint is that results seemed to be returning useless results when typing 1-2 characters. This stemmed from results being matched in the middle of words instead of at the start of the domain, for example. The adaptive learning helps avoid this problem because you’re typing words and selecting results that matched the word you wanted. The learning system then knows to show that selected page over others when you just type a single letter of the word — effectively showing a result that matches at the beginning of the word.

So to improve things for Beta 5, words that you type in the location bar will try to match on word boundaries e.g., matching after a forward slash or space. This even works for CamelCase (capitalizing the first letter of words instead of putting spaces) which is common for wikis.

Searching for “wik m” matching on word boundaries

Display

The first thing people will probably notice is that the list doesn’t feel as overpowering anymore. The number of results shown on the screen has been reduced to 6. Additionally the font size of the title text is smaller which felt unnecessarily large on some platforms like OS X. Ideally, the fewer number of results will help users scan results quickly instead of feeling overwhelmed. Combined with better functionality of multi-word search, adaptive learning, and word boundary matching, finding the page you want should be a happy experience. 🙂

Another set of changes is for how words you type get emphasized. Instead of only showing the first match in the title and url, it’ll emphasize all matches. Additionally, it’ll show matches when you type multiple words as well, so each word gets emphasized instead of nothing at all. For browser skin designers, there’s a new css class to alternatively emphasize matches, but the main purpose is to avoid styling bold which breaks common ligatures in some languages.

Bold/underline for english, just underline for ligatures

Performance

There has been improvements in browser responsiveness in Beta 5, so now it no longer eats up all of your CPU power for every letter that you type. In Beta 4, every single letter you typed caused the browser to start searching through your whole history

To optimize for users typing letters one by one for a whole word, we now reuse the results that are currently being shown in the list as well as continuing the search from where the last one left off. This has 2 main effects outside of reduced CPU usage: 1) existing matching results show up immediately instead of disappearing momentarily then reappearing and 2) not-as-frecently visited results can be found faster as you continue to type.

CPU usage when searching in Beta 4 and Beta 5

The picture shows a CPU usage graph where high bars means the CPU is doing a lot of work (and potentially not letting it update the UI). The horizontal axis is time and each set of 5 bars shows the 5 seconds after typing a letter one by one. So comparing the two graphs, we find the same results with a lot less work.

As an informal poll, I was wondering how many people are using the unofficial tryserver builds that I’ve been making. There’s some features like showing keyword searches, restricting searches, etc., that might not make it into Firefox 3 final, but I could potentially start a build near ship time, so you can get Firefox 3 + some extra awesomeness.